Method for producing derivatives of hexahydropyrimidine and converting the same to 1, 3-diamines



Patented Dec. 8, 1953 METHOD FOR PRODUCING DERIVATIVES OF HEXAHYDROPYRIMIDINE AND CON- VERTING THE SAME TO 1,3-DIAMINES Curtis W. Smith, Berkeley, Calif., assignor to Shell Development Company, Emeryville, Calif., a corporation of Delaware No Drawing. Application January 4, 1952,

Serial No. 265,058

12 Claims. (01. 260-251) This invention relates to a method for producing nitrogen-containing compounds, including various derivatives of hexahydropyrimidine, and to a method for decomposing said compounds to 1,3-diamines.

It is known that when an alpha,beta-unsaturated carbonylic compound (e. g., acrolein) is reacted with an excess of a urea-type compound in the presence of nitric acidor other suitable catalyst, the urea compound reacts with the ethylenic as well as the carbonylic bond of the carbonylic reactant. In such reactions one of the principal products comprises a heterocyclic compound of the type having the general formula wherein the R's, which may be the same or different, represent hydrogen atoms or organic radicals (preferably hydrocarbon radicals such as alkyl, aryl, alkaryl or aralkyl radicals) and the Xs represent x0, thio, or imino radicals. In addition, linear products, including those of the type having the general formula NR.OX.NHR

wherein the B's and Xs are as indicated above, and y isa small whole number of from 1 to about 5, are also produced.

The foregoing reaction has been described as one between a urea-type compound and an alpha, beta-unsaturated carbonylic reactant. The term urea-type compound is employed herein to,

designate compounds of the type having the general formula RHN.CX.NHR, wherein X represents either :0, :S or =NH, and the Rs, which may be the same or different, represent hydrogen atoms or organic radicals. Representative reac- R RoH=dt-R wherein the E5, which may be the same or dif- NRcXNHR ferent, represent hydrogen atoms or organi radicals, representative compounds being acrolein, crotonaldehyde, methacrolein, methyl vinyl ketone, beta-phenylacrolein, vinyl benzyl ketone, alpha-phenylacrolein, or the like. This reaction proceeds at ambient conditions of temperature and pressure, preferably in aqueous solution, and in the presence of nitric or other acid catalyst.

There is employed at least 1.5 moles of the ureatype reactant for each mole of the carbonylic reactant, and preferably about 2 moles of the urea compound are used per each mole of the carbonylic reactant. As the urea-carbonylic molar ratio becomes appreciably greater than about 3:1, the reaction becomes less efficient in the sense that a portion of the urea-type compound is not converted to the desired product compounds.

It has now been discovered that when one or more of the products obtained by reacting a ureatype compound with an alpha,beta-unsaturated carbonylic compound, as described above, is hydrogenated at elevated temperatures in the presence of a hydrogenation catalyst, at least one mole of the original urea-type reactant splits out for each mole of material hydrogenated, thereby forming valuable product compounds. In the case of the heterocyclic materials, the reaction obtained by hydrogenation can be represented by the following general equation:

wherein the His, which may be the same or different, represent hydrogen atoms or organic radicals, preferably hydrocarbon radicals such as alkyl, aryl, alkaryl or aralkyl radicals, and wherein the Xs represent oxo, thio or imino radicals. In the case of the linear starting materials, the reaction obtained by hydrogenation can be represented by the following general equation wherein the Rs and Xs are as indicated above, and y is a small whole number between 1 and 5.

Specific reactions which are illustrative of those which occur during hydrogenation are as follows: The formation of tetrahydro-2-pyrimidone (2-oxo-hexahydropyrimidine) by hydrogenation of -ureidotetrahydro-2pyrimidone (obtained by reacting lmole of acrolein with 2 moles of urea) the formation of tetrahydro-Z-thiopyrimidone (2-thiohexahydropyrimidine) by hydrogenation of 4-thioureidotetrahydro-2-thio pyrimidine (obtained by reacting 1 mole of acrolein with 2 moles of thiourea); the formation of 2-irninohexahydropyrimidine by hydrogenation of 4guanido-2-iminohexahydropyrimidine (obtained by reacting 1 mole of a'crolein with 2 moles of guanidine); the formation of 6-methyltetrahydro-2-pyrimidone by hydrogenation of 6- methyl-4-ureidotetrahydro-2-pyrimidone (obtained by reacting 1 mole of crotonaldehyde with 2 moles of urea) the formation of -methyltetrahydro-2-pyrimidone by hydrogenation of. 5- methyl 4 ureidotetrahydro-2-pyrimidone (obtained by reacting 1 mole of methacrolein with 2 moles of urea); and the formation of 4-methyltetrahydro-Z-pyrimidone by hydrogenation of 4- inethyl-l ureidotetrahydro-2-pyrimidone (obtained by reacting 1 mole of methyl vinyl ketone with 2 moles of urea).

A specific reaction which is illustrative of those a which occur during hydrogenation of linear products is as follows, the material undergoing hydrogenation here being the product obtained by reacting 1 mole of acrolein with 2 moles of urea.

NELC O.NH2

In conducting the hydrogenation reaction of the present invention, a solution of the material to be hydrogenated is treated with hydrogen in the presence of a hydrogenation catalyst at temperatures above about 75 0., the reaction being conducted. in either atmospheric or superatmospheric pressures. The hydrogenation step can be terminated whenever desired, though in the interest of efficiency of operation, the hydrogenation is continued until at least 1 mole of hydrogen has been absorbed for each mole of reactant compound. As hydrogenation catalyst there can be employed any material which is active as a hydrogenation-dehydrogenation catalyst. Suitable materials of this type include finely divided nickel or nickel deposited on kieselguhr or pumice, colloidal platinum, finely divided palladium, metallic chromium, alumina, iron oxidechromium oxide, copper oxide-chromium oxide compositions, and the like. The catalyst can be used in any suitable amount, the amount used being dependent upon the nature of the reactant, the character of the reactant substance, the operating conditions of the reaction, etc. In general, however, an amount of catalyst ranging from between about 0.5% and about 10%, based on the weight of reactants, gives satisfactory results.

. It has also been found that when one or more of the various heterocyclic and linear products obtained by a practice of the above-described hydrogenation step are subjected to hydrolysis in the presence of an acid or a base, these products are decomposed to 1,3.-.diam-ines. In the case of the heterocyclic products, the reaction which takes place during hydrolysis can be represented by the following general equation-z wherein the Rs and the Xs are as indicated above. In addition, there is also formed carbon dioxide, ammonia, carbon disulfide, or the like, depending upon whether the X is an oxo, thio, or imino group.

In the case of the linear reaction products, the reaction which occurs during hydrolysis can be represented by the following general equation:

RH.N.CX.NR (CHR.CHR.CHR.NR.CX.NR)1,H

' g RHNCHRCHRCHRNRH wherein the E5 and Xs are as indicated above and 3/ represents a small whole number between about 1 and 5. As was the case with the products obtained on hydrolyzing the heterocyclic starting materials, here again there will also be formed ammonia, together with carbon dioxide, and the like, depending on the nature of the group .re'pre" sented by X.

The hydrolysis reaction of the present invention is illustrated by a numberof specific reactions; thus, hydrolysis of tetrahydro-Z-pyrimidone yields 1,3-diaminopropane, and in a similar 1,3-diaminopropane is also obtained by hydrolysis of either tetrahydro-2-thiopyrimidone or 2-iminohexahydr-opyrimidine. Again, hydrolysis of 6- methyltetrahydro 2 pyrimidone yields 1,3 diaminobutane, while 1,3-diamino-2-methylpropane is formed by hydrolysis of 5-methyltetrahydro-Z-pyrimidone or the corresponding Z-thio or Z-imino-substituted starting materials.

As regards hydrolysis of linear reaction'products, a specific reaction is that wherein 1,3-diaminopropane is obtained by hydrolyzing the product obtained on hydrogenating the reaction product of 1 mole ofiacrolein with 2 moles of urea.

The conditions employed in the hydrolysis step of the present invention are those which are conventionally employed in other hydrolysis operations of this same general character. Thus, after addition of the acid or base material to an aqueous solution of the material undergoing hydrolysis, the solutionis heated at atmospheric or V superatmospheric pressures for the desired inter:

val of time. The diaminereaction productscan berecovered'from the ractionmixture by any one of several available procedures. In one recovery method, the amines are steam distilled from the reaction mixture and are thenrecoveredfrom the distillate by saturating the latter'with alkali followed by extraction with-ether. Another separation method is to. form acid saltsof the amine present in the reaction mixture and then to strip offthe water from the latter. The-remaining amine salts can: then. readily be converted int the amine condition.

It. has been brought out in the preceding portions of this application that in either or both. of the hydrogenation. and hydrolysis steps, there may be treated either single starting compounds or mixtures thereof. It should also be pointed out that good results are obtained by working with the reaction mixtures as a whole. That is to say, the reaction-mixture. obtained by reacting with sodium hydroxide.

l acidified and evaporated to dryness.

was liberated with 40% sodium hydroxide, extracted with ether, dried over solid sodium hy- Example I In this operation a solution was prepared containing 6 moles of urea, 9 grams of concentrated nitric acid and 360 grams of Water. To this solution there was slowly added 2 moles of acrolein, the temperature of the reaction mixture being maintained at about 65 C. by cooling. The reaction mixture so obtained was then neutralized To the solution was added a quantity of about 10 grams of Raney nickel, following which the solution was hydrogenated at 125C. to 155 C. and 1000 to 1500 p. s. i. g. until one mole of hydrogen was absorbed 'per mole of acrolein charged. Two-thirds of the resulting mixture was then separated for further working up. After removal of the catalyst by filtration, the filtrate was evaporated to drive off ammonia (formed onhydrolysis of urea) and water. and 68 grams of crystals were separated from the ethanol solution. Concentration of the mother liquor yielded an additional crop grams) of crystals. The total crude crystal crop so obtained was then recrystallized, once from ethanol and once from Water, there being recovered grams of pure crystalline tetrahydro-2-pyrimidone having a melting point of 259- 260 C., which corresponds with the known melting point of tetrahydro-2-pyrimidone. A small sample of the crystals, on being sublimed under vacuum, was found to have an elemental composition corresponding to that expected from this compound.

The mother liquor obtained after separating out the crystals as described above was a viscous, brown, Water-soluble syrup which was found to contain 36.87% carbon, 7.75% hydrogen and 29% nitrogen. From material balance and analysis of the syrup, it was concluded that the product was derived from urea and acrolein in the average molar ratio of 4:3, and that the composition was essentially made up of alternating trimethylene and urea units having the structure with y having an average value of about 3.

Example II A 208 gram portion (69%) of the reaction mixture obtained from the drop-Wise addition of 1 mole of acrolein to a solution containing 2 moles The residue was suspended in ethanol, L

*of urea and 6 grams of concentrated nitric acid in 120 grams of water, was neutralized with 7 sodium hydroxide and hydrogenated in the presence of 3 grams of Raney nickel at 150 C. and

:atmospheric pressure to hydrolyze the urea derivatives. out, steam was passed through the mixture to aid After the solids started separatin the distillation. The distillates were combined, The amine droxide and distilled, yielding 18.3 grams of 1,3- propanediamine boiling at l36l38 C. Extraction of the steam distillation residue with ethanol,

zfOHOWed by distillation of the ext ract, yielde d 6 another 8.1 grams of 1,3-propanedi'amine. Based on the amount of acrolein employed, the yield of diamine was 52%.

The products formed by the hydrogenation step of the present invention, as well as the 1,3- diamines formed on the hydrolysis of such products, are valuable compounds which are useful for a number of purposes in addition to their utility as intermediates.

The invention claimed is:

l. The process of forming a compound of the type having the general formula said process comprising reacting with molecular hydrogen a compound having the general formula under hydrogenating conditions at a temperature above C. but below that at which substantial pyrolysis occurs in the presence of a hydrogenation catalyst, the R's in said general formulae representing a member selected from the group consisting of the hydrogen atom and hydrocarbon radicals having one to seven carbon atoms and the Xs representing a member selected from the group consisting of 0x0, thio and iminoradicals.

2. The process of forming a tetrahydro-Z-pyrimidone comprising reacting with molecular hydrogen 4-ureidotetrahydro-2-pyrimidone under hydrogenating conditions at a temperature above about 75 C. but below that at which substantial pyrolysis occurs in the'presence of a hydrogenation catalyst.

' 3. The process of forming tetrahydro-2-thiopyrimidone comprising reacting with molecular hydrogen .4-thioureidotetrahydro-2-thiopyri1nidone under hydrogenating conditions at a temperature above 75 C. but below that at which substantial pyrolysis occurs in the presence of a hydrogenation catalyst. f

4. The process of forming 2-iminohexahydro pyrimidine comprising reacting with molecular hydrogen .4-guanido-2-iminohexahydropyrimidine under hydrogenating conditions at a temperature above 75 C. but below that at which substantial pyrolysis occurs in the presence of a hydrogenation catalyst.

5. In a method for producing a 1,3-diamine from at least one compound selected, from the group consisting of compounds of the general structure aecaocc and eompoundszof the general structure NROXJNHR R-HN.OX.NR.(OHR.O HR.JJR.NR.Q.X.N R),,,H

in which each R represents a radical selected from the group consisting of the hydrogen atom and hydrocarbon radicals having one to seven carbonatoms, each X represents a ,member of the group consisting of oxo, thio and imino radicals, and y is a small integer from 1 to 6, the steps comprising reacting molecular hydrogen with at least one of saidcompounds under hydrogenating conditions at a temperature above 75 C. but below that at which substantial pyrolysis occurs in the presence of a hydrogenation catalyst, and subjecting the product of said reaction step which is a member of the group consisting of compounds of the general structure and compounds of the general structure RHN.CX.NR. (CHRCHRZCHRNRCXNR) 11H to hydrolysis vin the presence of .a material selected from the group consisting of acids and bases. I

6. The method of claim 5 wherein the com- "pound hydrogenated is produced by reacting in the presence of a :mineral acid an alphametaunsaturated carbonyl-i0 compound of thegeneral structure with a molar excess of a urea-type compound of the general structure -R-N(J-III4R wherein the symbols .R and X have the same significance as in claim 5.

'7. 'The process wherein a compoundlof the general-formula .N-R.CX.NHR TREN=CX.-NR.(CHR;CHRe'RNRoXNRMH in which each 'R'represents a radical selected from the group consisting of the "hydrogenatom and hydrocarbon radicals having "one to "seven carbon atoms, each X represents a -member of "the group consisting of oxo, thio'and'imino radicals and y is'a small integer frorn'1'to'5, is'reacted with molecular hydrogen under hydro- "*genating-conditions at a temperature-above 75 C. butb'elow that at which substantial pyrolysis "occurs "in the presence of a hydrogenation catalyst, thereby forming a compound of the genera'l struct1-1re RHN.CX-.NR.(CI-IRCHRCHRNRCXNR);yH+

yNHR.CX.NHR,

8. In a method for producing 1,3-propanediamines, the steps com-prising reacting acrolein with a molar excess of a urea-type compound of the general structure wherein each H-Rrepresents :a radical selected from the group consisting of the hydrogen atom and hydrocarbon radicals having 1 to about ,ldcarbon atoms, and representsa member of the .group consisting of oxo, thio, and .slmino radicals, in the presence of a mineral acid, reacting the compound of the general structure produced thereby with molecular hydrogen under hydrogenating conditions at .a temperature ,aboye 75 C. but below that at which substantial pyrolysis occurs in the presence of .a hydrogenation catalyst, subjecting the product having the general structure wherein eachR represents a radical 'sel'ectedfrom the group consisting of the hydrogenatom iand hydrocarbonradica'ls having '1 to about 11) carbon atoms, and 'Xmepresents :a member of theng p consisting of oxo, .thio, and imino radicals, in the presence of a mineral acid, reactingthe compound of the general structure produced thereby with molecular hydrogen under --hydrogenati-ng conditions at I a temperature above 75 but below that at which substantial pyrolysis occurs in the presence of a hydrogenation --.catalyst, t-subiecting the product having the general structure group consisting v,cif acids land bases, andseparat- -.ing the .1,3=pr.opanediamine produced from 'the hydrolyzed reaction mixture.

.12. 'In a method for producing 1,3diamines, the steps comprising reacting an ,alpha;betaunsaturated gcarbonylic compound of the general structure Whereineach R represents a radical selected from the group consisting of the hydrogen atom and hydrocarbon radicals having 1 to about 10 carbon atoms, with a molar excess of urea in the presence of nitric acid, reacting the compound of the general structure ll 7 YHN/ \ITIHV 1'1 0 H-(J CN- NHz i H R thereby produced with molecular hydrogen under hydrogenating conditions in the presence of a hydrogenation catalyst at a temperature above 75 C. but below that at which substantial pyrolysis occurs, subjecting the product having the general structure References Cited in the file of this patent UNITED STATES PATENTS Name Date Haury Apr. 24, 1945 Haury Nov. 1, 1949 OTHER REFERENCES Bergmann et al., J. Org. Chem., vol. 13, pp. 353-356 (1948).

Number 

8. IN A METHOD FOR PRODUCING 1,3-PROPANEDIAMINES, THE STEPS COMPRISING REACTING ACROLEIN WITH A MOLAR EXCESS OF A UREA-TYPE COMPOUND OF THE GENERAL STRUCTURE 